FR3105840A1 - Detection component including black pixels and method of manufacturing such component - Google Patents

Abstract

The invention relates to an electromagnetic radiation detection component (1) comprising at least one mask (140) arranged to obscure electromagnetic radiation for at least one of the detection structures (122). The opaque mask (140) comprises a successive stack of a first metallic layer (141), a second metallic layer (142), a third transparent layer (143) of low optical index and a set of metallic elements (144). The second metallic layer (142), the transparent layer (143) and the set of metallic elements (144) form MIM structures in the wavelength range. The invention further relates to a method of manufacturing such a component (1) Figure for the abstract: Figure 1

Description

Detection component including black pixels and method of manufacturing such a component

The invention relates to the field of components for detecting electromagnetic radiation and in particular those aimed at detecting electromagnetic radiation in the infrared wavelength ranges.

Thus, the subject of the invention is a component for detecting electromagnetic radiation and a method for manufacturing such a component.

State of the prior art

In the context of applications for detecting weak electromagnetic signals, such as for spatial infrared radiation detection components, in order to better identify useful photonic signal with respect to noise, it is known, in particular from document US10326952, to provide an opaque mask above certain detection pixels of these components in order to measure, from these covered pixels, a dark current

Thus, with such a configuration taught by document US10326952, making it possible to determine the dark current and therefore the noise signal, it is possible to identify the relevant signal emerging from this noise.

Nevertheless, without precision on the configuration of the mask in the document US10326952, except that it is possible to provide, with an adequate material (chromium is mentioned), a mask with a thickness reduced to 1 μm, a mask as taught by this document is generally metallic and has a relatively large thickness, that is to say greater than or equal to 1 μm.

Thus, in the case of a detection component according to a configuration considered in which the component comprises a support comprising a layer, called active layer, in which is arranged a plurality of electromagnetic radiation detection structures, the support comprising a first face from which the active layer extends, and a second face, opposite the first face through which the support is intended to receive the electromagnetic radiation, and a mask arranged on the second face, the following phenomena are observed:
- shading due to the relatively large thickness of the masks,
- diffraction linked to the edges of the mask and which is the source of photon leakage towards the masked structures,
- spurious reflection in the enclosure containing the component and which may be the source of spurious signals.

It will also be noted that in the case of low temperature infrared radiation detection components, due to the thermal stresses to which they are subjected, may present, for opaque masks of relatively large thicknesses, significant risks of degradation and detachment. . In such use, the use of relatively thin opaque masks should make it possible to limit the risks of degradation and detachment.

The object of the invention is to at least partially solve the above drawbacks and thus aims to provide a detection component which, having the configuration considered, is only partially, or even not at all, subject to the phenomena of parasitic reflections present in the case of the prior art. The invention also aims, in particular in the context of detection components intended to operate at low temperature, to provide a detection component which can present an opaque mask less sensitive to the risks of degradation and detachment when the component is subjected to low temperature. .

The invention relates for this purpose to a component for detecting electromagnetic radiation in a range of wavelengths comprising:

- a support comprising a layer, called the active layer, in which is arranged a plurality of structures for detecting electromagnetic radiation in the said range of wavelengths, the support comprising a first face from which the active layer extends, and a second face, opposite the first face through which the support is intended to receive the electromagnetic radiation,

- at least one mask, called opaque mask, arranged on a portion of the second face of the support to conceal the electromagnetic radiation for at least one of the detection structures, called masked structure.

The opaque mask comprises at least a first, a second and a third metal and a material, called transparent material with a refractive index less than or equal to 2 in the wavelength range, the first metal having a coefficient of extinction k _m1 greater than or equal to 5n _m1 , or even 10n _m1 , and the second and third metal each having an extinction coefficient k _{m2 /3} less than or equal to 2n _{m2 /3} with n _m1 and n _{m2 /3} the indices refraction of the first and said second and third metal in the range of wavelengths, the transparent material having an extinction coefficient k _t less than or equal to 0.01.

The opaque mask comprises, from the second face of the support, a successive stack:

- a first metallic layer made from the first metal,

- a second metal layer made from the second metal,

- a third layer, called transparent layer, made of the transparent material, and

- a set of metal elements made of the third metal, said set being arranged on the transparent layer opposite the second metal layer,

and wherein the second metallic layer, the transparent layer and the set of metallic elements form MIM structures in the wavelength range.

With such a combination of MIM structures based on “absorbent” metal, i.e. having an extinction coefficient _km2 less than or equal to 2n _m2 , and a reflective layer based on “reflecting” metal, that is to say a metal having an extinction coefficient k _m1 greater than or equal to 5n _m1, makes it possible to benefit both from the occultation properties provided by the first metal and the first layer which is formed therefrom, and from antireflection properties provided by the MIM structure in the wavelength range. Thus, it is possible to provide a thin mask, limiting the shading phenomenon that such a mask could cause, and little or even no reflection, thus limiting the risks of parasitic reflections in the environment close to the component of detection and therefore the spurious signals associated with it.

In addition, such an opaque mask being able to present an opaque mask with a relatively low thickness compared to the opaque masks of the prior art, such as that disclosed by the document US10326952, the opaque mask of a component according to the invention has relatively low risk of degradation and detachment when the component is subjected to low temperature.

It is recalled that a metal is characterized by an electrical permittivity ε = (n+ik)² with n the refractive index of said metal and k the extinction coefficient. From this value, it is possible to calculate a skin thickness δ at a given wavelength λ from the following expression: δ= λ/(2πk).

MIM structures, for Metal/Insulation/Metal structure, are horizontal multi-layer cavities used in particular in the context of antennas. A MIM structure comprises a first metal layer coated with a transparent layer, generally dielectric, and a metal element, such as a metal stud, preferably made of the same metal as said first metal layer. In the classic application of such MIM structures, where relatively wavelength-selective cavity resonances are exploited, the metal of the first metal layer and of the set of metal elements is a metal having good reflectivity, c that is to say for which the extinction coefficient in the wavelength considered is greater than 10 times the refractive index of this same metal at the wavelength considered. More information about such MIM structures can be found in particular in the article published in 2006 by A.P. Hibbins and his co-authors in the scientific journal “Physical Review B” Number 74 pages 073408.

The second and the third metal can be identical.

With such a configuration, the absorption rate of the MIM structure is optimized.

The first metal layer may have a thickness h _m1 greater than 2 times a skin thickness δ _m1 of the first metal in the wavelength range, the thickness of the first metal layer preferably being greater than 4 times the thickness of skin δ _m1 of the first metal in the wavelength range.

In this way, the opaque mask has a particularly low transmission rate, or even substantially zero.

The second metal layer may have a thickness h _m2 of between 0.5 times a skin thickness δ _m2 of the second metal in the wavelength range and 4 times the skin thickness δ _m2 of the second metal in the range of wavelengths, the thickness of the first metal layer preferably being greater than 4 times the skin thickness δ _m1 of the first metal in the range of wavelengths.

The metal elements may have, along a plane substantially parallel to the second face, at least one lateral dimension L less than or equal to a value Lm respecting the following equation:

with λ ₀ a central wavelength of the range of wavelengths, n _d a refractive index of the transparent material at said wavelength, central h _d a thickness of the transparent layer and δ _m2 a skin thickness of the second metal at said wavelength,

the metallic elements preferably having a maximum lateral dimension and a minimum lateral dimension, along a plane substantially parallel to the second face, of between 0.75 times said Lm value and 1.25 times the Lm value.

MIM structures are thus particularly suitable for the wavelength range.

In the set of metallic elements, two adjacent metallic elements have between them an inter-barycenter distance less than or equal to λ ₀ /n _d , λ ₀ being a central wavelength of the range of wavelengths and n _d the refractive index of the transparent material in the range of wavelengths, the pitch P between two adjacent metallic elements in the set of metallic elements being preferably less than 0.75 times λ ₀ /n _d .

The metallic elements of the set of metallic elements can be arranged periodically with a pitch P between the metallic elements less than λ ₀ /n _d , said pitch P between the between the metallic elements being preferably less than 0.75 times λ ₀ / _nd .

The transparent layer may have a thickness between λ ₀ /4n _d and λ ₀ /25n _d , the values λ ₀ /4n _d and λ ₀ /25n _d being included, λ ₀ being a central wavelength of the range of wavelengths and n _d the refractive index of the transparent material in the wavelength range.

Each metallic element of the set of metallic elements can have a thickness, in the stacking direction of the opaque mask, which is between once a skin thickness δ _m2 of the third metal in the range of wavelengths and three times said skin thickness δ _m2 of the second metal, the thickness of each metal element being preferably between one and a half times the skin thickness δ _m2 of the third metal in the wavelength range and twice and half said skin thickness δ _m2 of the third metal.

With such parameters of the MIM structures, the rate of reflection of the opaque mask is particularly low or even substantially zero.

The opaque mask can be arranged on the second face of the support to obscure the electromagnetic radiation for the at least one masked structure and the detection structures adjacent to said at least one masked structure.

With such an arrangement, the possible collection of photo-carriers from the adjacent structures towards the masked structure which could take place due to the classic electrical cross-talk between adjacent pixels is limited.

the opaque mask can be arranged on the second face of the support to also obscure the electromagnetic radiation from the detection structures adjacent to said detection structures adjacent to said at least one masked structure.

With such an arrangement, the risks of possible collection of photocarriers from adjacent structures are substantially nil.

The support may have a thickness of less than 10 μm, the opaque mask extending, on either side of a projection of the masked structure on the second face of the support over a distance greater than 15 μm and preferably greater than 30 μm.

The detection structures of the plurality of detection structures can be arranged according to a matrix defining rows and columns of detection structure, the opaque mask is arranged to obscure the electromagnetic radiation for detection structures of the same row or column .

The invention further relates to a method of manufacturing a component for detecting electromagnetic radiation in a range of lengths comprising the following steps:

- provision of a support comprising a layer, called active layer, in which is arranged a plurality of structures for detecting electromagnetic radiation in said range of wavelengths, the support comprising a first face from which extends the active layer, and a second face, opposite the first face through which the support is intended to receive the electromagnetic radiation,

- formation of an opaque mask comprising, from the second face of the support, a successive stack:

o a first metallic layer made of a first metal,

o a second metallic layer made of a second metal,

o a third layer, called transparent layer, made of a material called transparent material with a refractive index less than or equal to 2 in the wavelength range, and

o a set of metallic elements made of a third metal, said set being arranged on the transparent layer opposite the second metallic layer, the second metallic layer, the transparent layer and the set of metallic elements forming MIM structures in the wavelength range,

the opaque mask being arranged on a portion of the second face of the support to obscure the electromagnetic radiation for at least one of the detection structures, called the masked structure,

in which process the opaque mask comprises the first, the second and the third metal and the material, called transparent material, the first metal having an extinction coefficient k _m1 greater than or equal to 5n _m1 , or even 10n _m1 , and the second metal having an extinction coefficient k _m2 less than or equal to 2n _m2 with n _m1 and n _m2 the refractive indices of the first and second metal in the wavelength range, the transparent material having a lower extinction coefficient k _t or equal to 0.01.

Such a method allows the manufacture of a detection component according to the invention and to benefit from the advantages associated therewith.

The formation stage includes the following sub-stages:

• deposition of the first metallic layer produced in the first metal in contact with the second face of the support,
• deposition of the second metal layer made in the second metal in contact with the first metal layer,
• deposition of the transparent layer, produced in the transparent material in contact with the second metallic layer, the third layer being called the transparent layer,
• formation of a set of metallic elements made in the third metal on the transparent layer opposite the second metallic layer.

During the step of forming the opaque mask, the mask is arranged on the second face of the support to obscure the electromagnetic radiation for the at least one masked structure and the detection structures adjacent to said at least one masked structure.

In this way, a component manufactured with such a method has, in operation, a masked structure little or not at all exposed to the leakage currents which could be generated by the adjacent structures if the latter were subjected to electromagnetic radiation.

The present invention will be better understood on reading the description of exemplary embodiments, given purely for information and in no way limiting, with reference to the appended drawings in which:

illustrates a side sectional view of the detection component according to the invention,

illustrates a close-up side sectional view of a detection component showing the arrangement of a masking element on a detection component according to the invention,

illustrates a top view of a masking element of a component according to the invention,

graphically illustrates the variation of the reflectivity of a masking element according to the invention as a function of the wavelength for different incidences of electromagnetic radiation,

graphically illustrates the variation of the reflectivity of a masking element according to a variant of the invention as a function of the wavelength,

graphically illustrates the absorption rate of a masked structure as a function of the thickness of the support divided by the refractive index of the support, this for two configurations of the opaque mask of the invention,

illustrates a first example of an arrangement of masking elements for a detection component in which masked reference structures are provided.

illustrates a first example of an arrangement of masking elements for a detection component in which masked reference structures are provided.

Identical, similar or equivalent parts of the different figures bear the same reference numerals so as to facilitate passage from one figure to another.

The different parts shown in the figures are not necessarily shown on a uniform scale, to make the figures more readable.

The different possibilities (variants and embodiments) must be understood as not mutually exclusive and can be combined with each other.

FIG. 1 illustrates a detection component according to the invention equipped with a so-called opacifying mask 140 arranged on a portion of the second face of a support 110 of the detection component 1 to completely obscure the electromagnetic radiation for at least one detection structures 122 of said detection component 1.

Such a detection component 1 is aimed more particularly at the detection of electromagnetic radiation in the infrared wavelength range. Thus, the different values indicated in the embodiments described below relate to this practical application, in which the target wavelength range is in a mid-infrared wavelength range, for example a range of wavelengths between 2.5 and 3.5 µm. Of course, those skilled in the art are perfectly capable, from the present disclosure, of adapting these values in order to allow, using such a detection structure 10, the optimized detection of electromagnetic radiation in a range of wavelengths other than infrared. In this context, the invention is particularly advantageous in the context of applications to the detection of electromagnetic radiation in the infrared wavelength ranges based on detection components operating at low temperature, i.e. that is to say typically less than -100°C or 173K, most often around 80K, as is the case for HgCdTe-based detectors.

Such a detection component 1 comprises:
- the support 110 comprising a layer 120, called active layer, in which is arranged a plurality of detection structures 121a, 121b, 122, 123 of electromagnetic radiation λ in said range of wavelengths, the support 110 comprising a first face from which the active layer 120 extends, and a second face, opposite the first face through which the support 110 is intended to receive the electromagnetic radiation λ,
- the opacifying mask 140 arranged on a portion of the second face of the support 110 to conceal the electromagnetic radiation from a detection structure 122 which is called a masked structure.

As shown in FIGS. 2A and 2B in the context of a variant of this embodiment in which the opacifying mask is arranged on a portion of the second face of the support 110 free of antireflection coating 130, the opacifying mask 140 comprises, at from the second face of the support 110, a successive stack:
- a first metal layer 141 made of a first metal,
- a second metal layer 142 made of a second metal,
- a third layer 143, called transparent layer, made of a transparent material, and
- a set of metal elements 144 made of the second metal, said set being arranged on the transparent layer 143 opposite the second metal layer 142.

The second metallic layer 142, the transparent layer 143 and the set of metallic elements 144 form MIM structures in the wavelength range.

The first metal has an extinction coefficient k _m2 greater than or equal to 5n _m1 and the second metal has an extinction coefficient k _m1 less than or equal to 2n _m2 with n _m1 and n _m2 the refractive indices of the first and second metal in the wavelength range. Preferably, the first metal has an extinction coefficient k _m2 greater than or equal to 10n _m1.

In this first embodiment, the first support 110 is a cadmium zinc telluride support CdZnTe comprising the active layer 120 made in a cadmium mercury telluride HgCdTe. Each of the detection structures 121A, 121B, 122, 123 is for example a PN photodiode, in accordance with those implemented in the prior art, these being shown only by their respective volume footprint occupied in the active layer.

Of course, if in this first embodiment, each detection structure 121A, 121B, 122, 123 is a PN photodiode, the invention is not limited to this type of detection structure alone. Thus, the component can, for example, comprise photodiodes of another type, such as PiN photodiodes (that is to say having an intrinsic zone formed between an N zone and a P zone), avalanche diodes or barrier, without departing from the scope of the invention.

The support 110 can have a thickness comprised between 1 and 20 μm, preferentially, between 5 and 15 μm. Thus, for example, the support may have a thickness of 10 μm.

The second face of the support 110 may comprise an antireflection coating 130 in accordance with the usual practice of those skilled in the art in the context of detection components 1 of the prior art. It will be noted that in the present embodiment, as illustrated in FIG. 1, the opaque mask 140 is arranged on the surface of this antireflection coating 130. Nevertheless, according to a variant shown in FIGS. 2A and 2B, the opaque mask 140 can be arranged on a portion of the second face of the support 110 free of antireflection coating 130. Indeed, due to the characteristics of the opaque mask 140, such an antireflection layer 130 is not necessary for the second face portions of the support 100 covered by an opaque mask 140.

The opaque mask 140 is arranged on the second face of the support 110, to obscure the electromagnetic radiation for at least one of the detection structures 122, called the masked structure. In order to perfect such occultation, as partially shown in FIG. 1, the opaque mask 140 can be arranged to occult the electromagnetic radiation for at least the masked structure 122 and at least one adjacent structure 123 on either side of it. this. Such a wider occultation makes it possible to limit the influence of the diffractive effects of the mask edges on the masked structure and to limit the possible collection of photocarriers from the zone 123 towards the structure 122 due to the classic electrical cross-talk between adjacent pixels. Such a configuration is explained further on in the following in connection with figure 2.

In the context of an application of the invention to near infrared and medium infrared, the first metallic layer 141 can be made of gold Au, aluminum Al or even copper Cu, or even an alloy of two metals, or even a alloy of these three metals.

It will be noted that, in particular in the case where the first metal is Au gold, there may be provided, between the second face of the support 110 and the first metal layer 141, a bonding layer of a few nanometers. Such a bonding layer can be, for the first metal which is gold Au, made of titanium Ti or nickel Ni.

The first metallic layer 141 preferably has a thickness h _m1 greater than 2 times a skin thickness δ _m1 of the first metal in the wavelength range, the thickness of the first metallic layer 141 preferably being greater than or equal to 4 times the skin thickness δ _m1 of the first metal in the wavelength range. It will also be noted that the thickness of the first metal layer is preferably less than 10δ _m1 .

In other words, the thickness h _m1 of the first metallic layer preferentially responds to the inequality 2δ _m1 < h _m1 < 10δ _m1 and responds, in a particularly advantageous manner, to the following inequality:

Thus, for example, the thickness h _m1 can be substantially equal to 4δ _m1 . In the case where the first metal is gold Au, the gold having, for a wavelength of 2.5 μm, a refractive index of 1.24, an extinction coefficient of 15.7 and therefore a skin thickness δ _m1 25 nm, a first metal layer 141 with a thickness of 100 nm is therefore obtained.

In the context of an application of the invention to the near infrared and to the middle infrared, the second metallic layer 142 can be made of titanium Ti or of platinum Pt, or of tungsten W, or even an alloy of titanium and platinum.

The second metal layer 142 has a thickness h_m2 between a 0.5 times a skin thickness δ_m2of the second metal in the wavelength range and at 4 times the skin thickness δ_m2of the second metal in the wavelength range. In other words, the thickness of the second metal layer 142 responds to the following equation:

Thus, for example, the thickness h _m2 can be of the order of the skin thickness of the second metal. In the case where the second metal is titanium Ti, the titanium Ti has, for a wavelength of 2.5 μm, a refractive index n _{m2 of} 4.36, an extinction coefficient of k _m2 of 3.19 and therefore a skin thickness titanium being 130 nm, a second metal layer 141 is therefore obtained of the order of 130 nm, that is to say between 100 nm and 160 nm.

The transparent layer 143 is made of a material, called transparent material, with a refractive index less than or equal to 2 in the wavelength range and having an extinction coefficient k_youless than or equal to 0.01 in the wavelength range. In a classic configuration of the invention, the layer of transparent material is made of a dielectric material, such as a silicon dioxide SiO₂, alumina Al₂O₃and magnesium fluoride MgF₂. As a variant, the layer of transparent material 143 can be made of a conductive oxide, such as an indium and tin oxide, better known by the acronym ITO, a zinc oxide, better known by the acronym ZnO and a aluminum-doped zinc oxide, better known by the acronym AZO. All of these materials have an extinction coefficient k_youless than or equal to 0.01 in the wavelength range.

It will be noted that, preferably, the material of the transparent layer 143 has a refractive index less than or equal to 1.5, which is particularly the case for silicon dioxide SiO₂, alumina Al₂O₃and magnesium fluoride MgF₂.

The transparent layer 143 may have a thickness Ep_dbetween λ₀/4n_dand λ₀/25n_d, the values λ₀/4n_dand λ₀/25n_dbeing included, λ₀being a central wavelength of the wavelength range and n_dthe refractive index of the transparent material 143 in the wavelength range. In other words the thickness Ep_dtransparent layer 143 can satisfy the following inequalities:

Thus, for example, the thickness Ep _d of the transparent layer 143 can be equal to λ ₀ /10n _d.

The set of metal elements 144 are arranged on the third layer 143 and are made in the second metal. Each metal element 144 of said assembly is in the form of a metal stud which can take, for example and according to a projection on the second face of the support 110, a square or circular, or even hexagonal shape.

Each metal element 144 preferably has, along a plane parallel to the second face, at least one lateral dimension L _em , such that, for metal elements 144 having a projection on the second face of the square support, a length of one side, for metal elements 144 having a projection on the second face of the circular support, a diameter which is preferably less than or equal to a value Lm respecting the following equation:

with λ ₀ a central wavelength of the range of wavelengths, n _d an index of refraction of the transparent material at said central wavelength, h _d the thickness of the transparent layer and δ _m2 the thickness skin of the second metal at said central wavelength.

It will be noted that in a particularly advantageous manner, the metal elements 144 have, along the plane substantially parallel to the second face, a maximum lateral dimension and a minimum lateral dimension, both of which are between 0.75 times the value Lm and 1.25 times the Lm value.

According to a first possibility of the invention, the metal elements can have a non-periodic arrangement with a spacing between two adjacent metal elements preferably having a pitch P less than or equal to λ ₀ /n _d , λ ₀ being a central wavelength of the wavelength range and n _d the refractive index of the transparent material in the wavelength range. In a particularly advantageous manner, the pitch P between two adjacent metal elements 144 in the set of metal elements 144 is less than 0.75 times λ ₀ /n _d .

According to a second possibility of the invention, the metallic elements 144 can have a periodic arrangement with a lattice pitch P less than or equal to λ ₀ /n _d , the lattice pitch being preferably less than 0.75 times λ ₀ /n _d . It will be noted that according to this second possibility, the metallic elements can be arranged in a square lattice with the lattice pitch P.

It will be noted that, in the case of a second non-noble metal, such as titanium Ti, in order to limit the risks of oxidation, it is possible, according to a possibility not illustrated, to provide for the deposition of a passivation layer of a few nanometers on the metallic elements 144. Thus, for example and for a second titanium metal Ti, it is possible that the metallic elements 144 are covered by a passivation layer of silicon nitride SiN or zinc sulphide ZnS of a thickness between 5 and 30 nm. Such a passivation layer can thus for example have a thickness of 10 nm.

Moreover, within the framework of the choice of the first and second metals, and of the transparent material for applications of a detection component 1 cooled to relatively low temperature, that is to say typically less than -100° C. or 173 K , these materials can be chosen with similar coefficients of thermal expansion. According to this possibility, the first metal can be platinum Pt, the second metal titanium Ti and the transparent material can be an amorphous silicon dioxide a-SiO ₂ , these materials having a thermal expansion coefficient of the order of 9.10 ^{- 6K -1} .

As a variant to this present embodiment, the metal elements can be made of a third metal. According to this variant, the third metal is chosen in such a way that, like the second metal, it has an extinction coefficient k _m3 less than or equal to 2n _m3 , n _m3 being the refractive index of the third metal in the wavelength range. Thus, in the context of an application of the invention to the near infrared and to the middle infrared, the third metal can be titanium Ti or Latin Pt, or even tungsten W, or even an alloy of titanium and platinum.

Thus, in a practical example of this first embodiment, for a range of wavelengths centered around a central wavelength λ ₀ of 2.7 μm, the opaque mask 140 can have the following characteristics:
- a first metal layer 141 made of titanium Ti with a thickness h _m1 of 150 nm,
- a second metallic layer 142 made of Au gold with a thickness h _m2 of 100 nm,
- a third transparent layer 143 made of silicon dioxide SiO ₂ with a thickness h _d of 120 nm,
- a set of metallic elements 144 in which the metallic elements present a projection on the second face of the square-shaped support with a side length L _em of 450 nm, and a thickness h _em of 200 nm, the metallic elements being arranged according to a square grating with a pitch P of 800nm.

The simulations of such an opaque mask 140 carried out by the inventors according to the modal method by Fourier development, of coupled waves better known by the English acronym RCWA for Rigorous Coupled-Waves Analysis, make it possible to show that such a mask has, as shown in Figure 3A, a transmittance over a wavelength range from at least 1.5µm to 5µm Less than 5.10 ^-6 and a reflectivity of less than 2% over a length range from 2.45µm to 3.1µm with a minimum of 0.03% for the central length of 2.7µm.

In order to demonstrate the small variation in the reflectivity R of such an opaque mask 140 with the angle of incidence of the electromagnetic radiation λ, FIG. 3A graphically illustrates the variation in the reflectivity of such an opaque mask 140 as a function of the wavelength of the electromagnetic radiation obtained for, under the reference 201, an electromagnetic radiation arriving on the second face with a normal incidence, under the reference 202, an electromagnetic radiation arriving on the second face with an incidence at 30° from the normal and a transverse electric polarization, that is to say with an electric field parallel to the second face of the support, and under the reference 203, electromagnetic radiation arriving on the second face with an incidence at 30° from the normal and a transverse magnetic polarization.

It can thus be seen that in the wavelength range from 2.45µm to 3.1µm and regardless of the polarization and the incidence of the electromagnetic radiation, the reflectivity remains below 0.02.

Furthermore, it is possible to optimize the opaque mask 140 in order to obtain a larger range of wavelengths for which the reflectivity remains below 5%. Thus, if we take the opaque mask 140 according to the previous example and for which the metal elements 144 have a lateral dimension L _em equal to 500 nm, a thickness h _em equal to 225 nm and a grating pitch P of 1.1 μm , and the transparent layer 143 has a thickness h _d of 140 nm, it is possible to obtain, in accordance with the inventors' simulations, a variation in reflectivity 211 as illustrated in FIG. 3B. With such a configuration, the reflectivity over a wavelength range from 1.1 μm to 3.3 μm remains below 6.5%.

According to the invention and in order to avoid any optical leaks on the masked structure 122 which could originate from diffraction phenomena linked to the edges of the opaque mask 140, it is possible to arrange the opaque mask 140 on the second face of the support 110 to obscure the electromagnetic radiation λ for the at least one masked structure 122 and certain detection structures 123 adjacent to said at least one masked structure 122. Such a possibility also makes it possible to limit the phenomena of leakage currents which may exist in a such detection component 1 between the detection structures and which could therefore interfere with the noise signal measured by the masked structure.

In order to illustrate this phenomenon, as shown in FIG. 4, the inventors have calculated the absorption signal A for, under the reference 221, a masked structure 122 whose directly adjacent structures 123 are also covered by the opaque mask 140 according to the practical example, and under the reference 222, a masked structure 122 whose directly adjacent structures and those which are adjacent to them are also covered by the opaque mask 140 according to the practical example, this according to a thickness of the support 110 divided by its refractive index. This absorption signal A includes both the absorption signal of the masked structure linked to the diffraction phenomena and to the leakage currents between the detection structures 122, 123. In this configuration simulated by the inventors, it was considered an arrangement of the structures in a matrix with a grating pitch of 15 μm.

It can thus be seen that, for a support 110 made of cadmium zinc telluride and CdZnTe with a thickness of 10 μm, that is to say a support thickness to refractive index ratio of 7.5, it is necessary that the structures directly adjacent and those which are adjacent to them are also covered by the opaque mask 140 to obtain an absorption of less than 0.1%.

Thus, in accordance with the calculations made by the inventors, it is therefore possible, for a detection component 1 comprising a support 10 μm thick and with an opaque mask 140 which extends, on either side of a projection of the masked structure 122 on the second face, over a distance greater than 30 μm (that is to say 2 adjacent pixels of 15 μm side), for a distance greater than 15 μm this absorption remains less than 0.1%. With this same support thickness, for such a distance greater than 15µm (i.e. 1 single adjacent pixel of 15µm side), this absorption remains less than 0.15%.

FIGS. 5A and 5B illustrate two examples of implementation of such an opaque mask 140 within the framework of a detection component comprising a matrix of detection structures 121, 122, 124. These figures illustrate the positioning of the mask or masks opaque with respect to the projection of the matrix of the detection structures on the second face of the support 110.

According to the first example illustrated in FIG. 5A, it is conceivable to use an opaque mask 140 arranged to conceal the electromagnetic radiation for masked structures 122 individual. According to this possibility, the detection component comprises a plurality of opaque masks 140 each corresponding to a respective masked structure 122 and the corresponding adjacent structures 123.

According to the second preferred example and illustrated in FIG. 5B, the detection component 1 can comprise a single opaque mask 140 arranged to obscure the electromagnetic radiation for a plurality of masked structures 122 arranged on one edge of the matrix of detection structures. Thus, according to this example, the opaque mask is arranged opposite a column of five detection structures 122, 123 extending along said edge, the third detection structure 122 of said column corresponding to the masked structure. Thus, according to this possibility, the detection component has a line of masked structures making it possible to provide a precise mean noise level since it is calculated on a large number of masked structures 122.

A detection component 1 according to this first embodiment can be manufactured using a method comprising the following steps:
- supply of a support 110 comprising a layer 120, called active layer, in which is arranged a plurality of detection structures 121a, 121b, 122, 123 of electromagnetic radiation λ in said range of wavelengths, the support 110 comprising a first face from which the active layer 120 extends, and a second face, opposite the first face through which the support 110 is intended to receive the electromagnetic radiation λ,
- deposition of the first metal layer 141 made in the first metal in contact with the second face of the support 110,
- deposition of the second metal layer 142 made in the second metal in contact with the first metal layer 141,
- deposition of the transparent layer 143, made of the transparent material in contact with the second metallic layer 142, the third layer 143 being called the transparent layer,
- formation of a set of metal elements 144 made in the second metal on the transparent layer 143 opposite the second metal layer 142.

It will be noted that the step of forming the set of metal elements 144 may include a sub-step of depositing a fourth layer of the second metal with a thickness h _em and a sub-step of localized etching, for example through an optical lithography, to keep only the parts of the fourth layer corresponding to the metallic elements 144.

Claims (16)

Component for detecting (1) electromagnetic radiation (λ) in a range of wavelengths comprising:
- a support (110) comprising a layer (120), called the active layer, in which is arranged a plurality of detection structures (121a, 121b, 122, 123) of electromagnetic radiation (λ) in said range of wavelengths , the support (110) comprising a first face from which the active layer (120) extends, and a second face, opposite the first face, through which the support (110) is intended to receive the electromagnetic radiation ( λ),
- at least one mask (140), called opaque mask, arranged on a portion of the second face of the support (110) to conceal electromagnetic radiation for at least one of the detection structures (122), called masked structure,
The detection component (1) being characterized in that the opaque mask (140) comprises at least a first, a second and a third metal and a material, called transparent material, with a refractive index less than or equal to 2 in the range of wavelengths, the first metal having an extinction coefficient k _m1 greater than or equal to 5n _m1 , or even 10n _m1 , and the second and the third metal each having an extinction coefficient k _{m2 /3} less than or equal to 2n _{m2 /3} with n _m1 and n _{m2 / 3} the refractive indices of the first and said second and third metal in the wavelength range, the transparent material having an extinction coefficient k _t less than or equal to 0, 01,
in which the opaque mask (140) comprises, starting from the second face of the support (110), a successive stack:
- a first metal layer (141) made from the first metal,
- a second metal layer (142) made from the second metal,
- a third layer (143), called transparent layer, made of the transparent material, and
- a set of metal elements (144) made of the third metal, said set being arranged on the transparent layer (143) opposite the second metal layer (142),
and wherein the second metallic layer (142), the transparent layer (143) and the set of metallic elements (144) form MIM structures in the wavelength range. Sensing component (1) according to claim 1, wherein the second and the third metal are identical. Detection component (1) according to Claim 1 or 2, in which the first metallic layer (141) has a thickness h_m1greater than twice a skin thickness δ_m1 of the first metal in the wavelength range, the thickness of the first metal layer (141) preferably being greater than 4 times the skin thickness δ_m1of the first metal in the wavelength range. Detection component (1) according to any one of Claims 1 to 3, in which the second metallic layer (142) has a thickness h_m2between 0.5 times a skin thickness δ_m2of the second metal in the wavelength range and at 4 times the skin thickness δ_m2of the second metal in the wavelength range, the thickness of the first metal layer (141) preferably being greater than 4 times the skin thickness δ_m1 of the first metal in the wavelength range. Detection component (1) according to Claim 2 alone or in combination with Claim 3 or 4, in which the metal elements (144) have, along a plane substantially parallel to the second face, at least one lateral dimension L less than or equal to at a value Lm respecting the following equation:

with λ ₀ a central wavelength of the range of wavelengths, n _d a refractive index of the transparent material at said wavelength, h _d a thickness of the transparent layer and δ _m2 a skin thickness of the second metal at said wavelength,
the metal elements (144) preferably having a maximum lateral dimension and a minimum lateral dimension, along a plane substantially parallel to the second face, comprised between 0.75 times said value Lm and 1.25 times the value Lm. Detection component (1) according to any one of Claims 1 to 5, in which in the set of metallic elements (144), two adjacent metallic elements (144) have between them an inter-barycentre distance less than or equal to λ ₀ /n _d , λ ₀ being a central wavelength of the wavelength range and n _d the refractive index of the transparent material in the wavelength range, the pitch P between two metallic elements (144) adjacent in the set of metal elements (144) being preferably less than 0.75 times λ ₀ /n _d . Detection component (1) according to claim 6, in which the metal elements (144) of the set of metal elements (144) are arranged periodically with a pitch P between the metal elements (144) less than λ ₀ /n _d , said pitch P between the between the metal elements (144) preferably being less than 0.75 times λ ₀ /n _d . Detection component (1) according to any one of Claims 1 to 6, in which the transparent layer (143) has a thickness of between λ ₀ /4n _d and λ ₀ /25n _d , the values λ ₀ /4n _d and λ ₀ /25n _d being included, λ ₀ being a central wavelength of the range of wavelengths and n _d the index of refraction of the transparent material (143) in the range of wavelengths. Detection component (1) according to Claim 2 taken alone or in combination with any one of Claims 3 to 8, in which each metallic element (144) of the set of metallic elements (144) has a thickness, in the stacking direction of the opaque mask (140), which is between once a skin thickness δ _m2 of the third metal in the wavelength range and three times said skin thickness δ _m2 of the second metal, the thickness of each metal element being preferably between one and a half times the skin thickness δ _m2 of the third metal in the wavelength range and two and a half times said skin thickness δ _m2 of the third metal. Detection component (1) according to any one of Claims 1 to 9, in which the opaque mask (140) is arranged on the second face of the support (110) to mask the electromagnetic radiation (λ) for the at least one masked structure (122) and the detection structures (123) adjacent to said at least one masked structure (122). Detection component (1) according to claim 10, in which the opaque mask (140) is arranged on the second face of the support (110) to also conceal the electromagnetic radiation (λ) from the detection structures (123) adjacent to the said detection (123) adjacent to said at least one masked structure (122). Detection component (1) according to Claim 10 or 11, in which the support (110) has a thickness of less than 10 µm and in which the opaque mask (140) extends, on either side of a projection of the masked structure (122) on the second face of the support (110) over a distance greater than 15 μm and preferably greater than 30 μm. Detection component (1) according to any one of claims 1 to 12, in which the detection structures (121, 122, 123) of the plurality of detection structures (121, 122, 123) are arranged according to a matrix defining rows and columns of detection structure, the opaque mask (140) is arranged to obscure the electromagnetic radiation for detection structures (122) of the same row or column. Method of manufacturing a detection component (1) of electromagnetic radiation (λ) in a range of lengths comprising the following steps:
- provision of a support (110) comprising a layer (120), called the active layer, in which is arranged a plurality of detection structures (121a, 121b, 122, 123) of electromagnetic radiation (λ) in said range of lengths waveform, the support (110) comprising a first face from which the active layer (120) extends, and a second face, opposite the first face through which the support (110) is intended to receive the radiation electromagnetic(λ),
- formation of an opaque mask (140) comprising, from the second face of the support (110), a successive stack:
o a first metal layer (141) made of a first metal,
o a second metal layer (142) made of a second metal,
o a third layer (143), called transparent layer, made of a material called transparent material with a refractive index less than or equal to 2 in the wavelength range, and
o a set of metal elements (144) made of a third metal, said set being arranged on the transparent layer (143) opposite the second metal layer (142), the second metal layer (142), the transparent layer (143) and the set of metallic elements (144) forming MIM structures in the wavelength range,
the opaque mask (140) being arranged on a portion of the second face of the support (110) to obscure the electromagnetic radiation for at least one of the detection structures (122), called the masked structure,
in which method the opaque mask (140) comprises the first, the second and the third metal and the material, called transparent material, the first metal having an extinction coefficient k _m1 greater than or equal to 5n _m1 , or even 10n _m1 , and the second metal having an extinction coefficient k _m2 less than or equal to 2n _m2 with n _m1 and n _m2 being the indices of refraction of the first and the second metal in the wavelength range, the transparent material having an extinction coefficient k _t less than or equal to 0.01. Manufacturing process according to claim 12, in which the forming step comprises the following sub-steps:

• deposition of the first metal layer (141) produced in the first metal in contact with the second face of the support (110),
• deposition of the second metal layer (142) made in the second metal in contact with the first metal layer (141),
• deposition of the transparent layer (143), made of the transparent material in contact with the second metallic layer (142), the third layer (143) being called the transparent layer,
• forming a set of metallic elements (144) made of the third metal on the transparent layer (143) opposite the second metallic layer (142).

Manufacturing process according to claim 14 or 15, in which during the step of forming the opaque mask (140), the mask is arranged on the second face of the support (110) to obscure the electromagnetic radiation (λ) for the at least one masked structure (122) and the detection structures (123) adjacent to said at least one masked structure (122).